The present invention relates generally to gas turbine engines and, more particularly, to coolable hollow turbine blades thereof.
The efficiency of a gas turbine engine is directly proportional to the temperature of turbine gases channeled through a high-pressure turbine nozzle from a combustor of the engine and flowable over turbine blades thereof. For example, for gas turbine engines having relatively large turbine blades, e.g., root-to-tip dimensions greater than about 1.5 inches, turbine gas temperatures approaching 2,700 degrees F. are typical. To withstand this relatively high gas temperature, these large blades are manufactured from known advanced materials and typically include known state-of-the-art type cooling features.
A turbine blade is typically cooled using a coolant such as compressor discharge air which is utilized in various structural elements for obtaining film, impingement, and/or convection cooling of the turbine blade. The blade typically includes a serpentine coolant passage and various cooling features such as turbulence promoting ribs, i.e. turbulators, extending from sidewalls of the blade into the serpentine passage to about 0.010 inches. Generally cylindrical pins may also be utilized and may extend partly or completely between opposing sidewalls of the blade in the serpentine passage.
The leading edge of a blade is typically the most critical portion thereof and special, relatively complex cooling features are used. For example, the leading edge typically includes leading edge cooling apertures which are effective for generating film cooling, or the serpentine passage at the leading edge may include impingement inserts for providing enhanced cooling, or the serpentine passage at the leading edge may include turbulators and pins for improving heat transfer.
Gas turbine engines which include relatively small turbine blades, e.g., less than about 1.5 inches from root to tip, have been unable to utilize many of the above described large blade cooling features because of their relatively small size and, therefore, these engines have been limited to about 2,300 degrees F. turbine gas temperature. It follows, therefore, that the small gas turbine engines have been unable to achieve the higher efficiency of operation associated with the higher turbine gas temperatures in the range of about 2,300 degrees F. to about 2,700 degrees F.
Accordingly, it is one object of the present invention to provide a turbine blade having new and improved cooling features.
It is another object of the present invention to provide small turbine blades with new and improved cooling features effective for withstanding turbine gas temperatures greater than about 2,300 degrees F.
Another object of the present invention is to provide a small turbine blade with cooling features having improved heat transfer coefficients.
Another object of the present invention is to provide a new and improved small turbine blade utilizing relatively simple and easily manufacturable cooling features.